Span Slab Research Articles

Load Distribution in Reinforced Concrete Slab Span Bridges

Load Distribution in Reinforced Concrete Slab Span Bridges

Experimental and numerical investigation on the flexural behavior of a novel composite slab with a joint

Composite slab has extensive application in building industrialization. In this study, a novel composite slab with a joint was proposed, where the precast planks with bent-up rebar are only partially prefabricated along the thickness direction at the joint for cast-in-site pouring of concrete, and the rest is fully prefabricated in the factory. The flexural performance of the composite slab was compared with that of a traditional cast-in-site slab with the same geometric dimensions through four-point bending test. The results demonstrate that the bending performance of the composite slab, including cracking load, yield load, and ultimate load, is basically consistent with that of the cast-in-site slab, and can meet the engineering requirements. Based on experimental results, numerical research was conducted on the composite slabs. The effects of slab thickness, diameter of steel bar, concrete strength of precast plank, and slab span on the flexural behavior of composite slab were investigated. The numerical results show that the cracking load, yield load, and load corresponding to the deflection limit of the specimen increase with the increase in slab thickness and decrease with the increase in slab span. Increasing the steel bar diameter can increase the load corresponding to the deflection limit and yield load, while the effect on the cracking load is almost negligible. The concrete strength of precast plank has no significant effect on the flexural behavior of the composite slab.

Experimental investigation on the thermal behavior of two typical stainless steel roof systems

SummaryUnder long‐term exposure to solar radiation and temperature difference, metal roof systems produce a noticeable thermal behavior. The thermal behavior experiment of two typical metal roof systems in engineering was studied. The temperature stress and displacement of the two typical metal roof systems under different influencing factors are compared and analyzed. The results show that the thermal behavior of the stainless steel roof system is significant. The peak stress accounts for about 69.9% of the stainless steel yield strength, and the peak displacement accounts for 3/3500 of the slab span. The loading rate and temperature difference greatly influence the thermal behavior of the two typical roof systems. The maximum influence of temperature difference and loading rate on the thermal behavior is 77.8% and 67.3%, respectively. The holding temperature time has a minor influence on the thermal behavior of the two typical roof systems, and the maximum influence range is less than 7%. The research conclusions provide a valuable reference for the thermal design of metal roof systems.

Flexural behavior of high strength concrete shallow wide beams reinforced by hybrid longitudinal reinforcement

ABSTRACT One of the most common statistical systems used in structures especially for wide span slabs are ribbed slabs with shallow wide beams (SWB). This experimental study aimed to investigate and enhance the flexural behavior of high-strength concrete SWB using hybrid longitudinal reinforcement from steel and advanced composite materials as a tensile main reinforcement in SWB. Longitudinal advanced composite bars locally manufactured from ribbed glass fiber reinforced polymer (GFRP) and the second type was ribbed basalt fiber reinforced polymer (BFRP). A group of six half scale SWB were examined in structures laboratory of American University in Cairo with dimensions 2.1 × 0.6 × 0.25 m for length (L), width (B) and depth (d) respectively with constant size effect (d/B). The first three specimens were completely reinforced at tension side with Steel, GFRP or BFRP ribbed bars to be considered a control specimen. Use of GFRP and BFRP bars enhanced the flexural capacity of SWB with 41% and 43% respectively compared to specimen completely reinforced with steel. But on the other hand, the crack propagation of specimens completely reinforced with GFRP and BFRP developed more quickly and had larger crack width compared to specimen completely reinforced with steel. Hybrid reinforcement from Steel with GFRP, Steel with BFRP and Steel with GFRP and BFRP specimens are used to enhance the crack pattern and mode of failure without a significant loss in flexural capacity of SWB. The flexural capacity of these three specimens was enhanced with 26%, 30% and 41% with a significant enhancement in crack pattern and ductility.

A New Analytical Method for Link Slab Analysis

Link slabs have been widely used to reduce the number of expansion joints. However, traditional reinforced concrete link slabs are prone to cracking issues, making it crucial to accurately calculate their internal forces. Currently, the most advanced link slab analysis methods treat the link slab and adjacent span as a rotational spring to simulate their restriction on the girder end rotation. However, this method does not comprehensively consider the link slab's influence, leading to conservative results. To address this issue, this study further considers the influence of girder end deformations on adjacent span, resulting in more accurate calculations of the link slab's internal forces. Additionally, the concept of the girder end rotation reduction coefficient is put forward for the first time, which provides a clearer and more quantified understanding of the link slab's influence. The proposed method is verified by a model test and a site test, which shows a significant improvement in accuracy compared to existing analytical methods. On this basis, a parametric study is conducted to investigate the influence of various parameters on the girder end rotation reduction coefficient, which indicates that span length, girder spacing, and support configuration have the greatest influence.

Slab Reinforcement Contributions to Negative Moment Strength of Reinforced Concrete T-Beam with High Strength Steel at Exterior Beam-Column Joints

Previous studies have revealed that the contribution of slab reinforcement to the T-beam flexural strength in negative moment regions are not negligible for the seismic capacity design. An effective slab width (i.e., effective width of flanged section) has been proposed, within which the slab reinforcement needs to be included in the calculation of the beam nominal flexural strength in negative moment regions. These studies mainly focused on the cases using normal-strength steel in moment resisting frames. However, recently high-strength steel has been widely used in reinforced concrete moment resisting frames in high seismic regions to avoid congestion near beam-column joints. The use of high-strength steel may affect the beam stiffness due to the fact that it will require less amount of reinforcement, and result in a different normal stress distribution compared to the case with normal-strength steel. Therefore, this paper investigates the slab reinforcement contribution to the flexural strength of the reinforced concrete T-beam designed with high-strength steel in negative moment regions at exterior beam-column joints, for which nonlinear pushover analyses were conducted. Beam reinforcement grade was considered as a primary parameter with several other design variables including slab thickness, height, and span length of the beam. Analytical results show that the use of high-strength steel can result in a wider effective slab width than the case of normal-strength steel for calculating the beam nominal flexural strength under the negative moment. Based on these results, new design equations were proposed.

Blast resistance of ECC and composite slabs subjected to near-field explosion

Due to the unfavorable blast resistance of reinforced concrete (RC) slabs, particularly with the frequent occurrence of penetration and spalling damage, engineered cementitious composite (ECC) provided a promising alternative for enhanced blast resistance through its direct application as a building material or by reinforcing existing RC slabs due to its excellent tensile ductility and toughness. In the present study, the blast resistance of the RC slab, the ECC slab, and the composite slab (RC slab reinforced by ECC layer) was investigated and compared through experimental and numerical approaches. Firstly, the material properties of the ECC were acquired through the quasi-static compressive test, as well as quasi-static and dynamic tensile tests, which felicitated the parameter calibration in the K&C model for ECC. Then the numerical models of the RC slab, the ECC slab, and the RC/ECC composite slab were established and validated with the blast test results. The test and numerical results showed that the ECC and composite slabs exhibited superior anti-blast performance in terms of failure mode, damage extent, and load mitigation compared to the RC slab. Owing to the remarkable ductility and toughness, the ECC and composite slabs could greatly reduce the possibility and severity of penetration and spalling damage. Furthermore, five significant parameters impacting the blast resistance of ECC and composite slabs were summarized through dimensional analysis including the tensile strength of ECC σt, the total explosive energy Q, the standoff distance R, the slab thickness H, and the slab span L. Then a dimensionless number was proposed to determine the failure mode and predict the residual deflection at the center of the ECC and composite slabs. The results could serve as a reference for the design of ECC and composite slabs to resist blast loading in the field of structural protection.

Structural behaviour of steel fibre-reinforced concrete floor system for modular construction

Steel fibre-reinforced concrete (SFRC) slabs are ideal for modular construction owing to the shorter span of slab in standardised modules. To investigate the structural behaviours of SFRC floor system designed for modular construction, nine full-scale slab specimens were tested both at ambient temperature and under fire conditions. The crack pattern, failure mode, concrete spalling phenomenon, deformation capacity, load-carrying capacity and fire resistance time of the SFRC slabs are reported and compared with those of conventional steel rebar-reinforced concrete slabs. The experimental results showed that SFRC slabs achieved sufficient load carrying-capacity and fire resistance time for the application in modular buildings. A fibre-element model is proposed for computing the temperature distribution and cross-sectional moment resistance of SFRC slabs under fire conditions. Based on the experimental findings, design recommendations are provided to determine the fire resistance of SFRC floor system in modular construction.

Research on Carbon Emission of Prefabricated Structure in China

The comparison of carbon emissions between prefabricated and traditional cast-in-place construction methods in actual example buildings has yielded inconsistent results due to the difficulty in accounting for design parameter uncertainty. Additionally, the carbon-reduction capacity of prefabricated structures remains a topic of debate. This paper investigates the carbon emission reduction capacity of prefabricated concrete frame structures compared to traditional cast-in-place structures, with a focus on addressing design parameter uncertainty. A quantitative model of carbon emissions is established using the subproject quota method and PKPM-PC software. The study evaluates the impact of design parameters, such as slab span and seismic requirements, and calculation parameters, such as carbon emission factor and transport distance, on carbon emissions. The results indicate that prefabricated structures with a higher assembly rate exhibit a stronger emission reduction capacity, mainly due to lower demands for labor and mechanical energy consumption. The study also highlights that prefabricated structures with smaller slab spans and higher seismic requirements have lower carbon emission reduction capacities and can produce greater carbon emissions than cast-in-place structures. Furthermore, the appropriate carbon emission factor for the material used in prefabricated structures is crucial for achieving reliable carbon reduction rates. Finally, the study emphasizes the importance of considering transport as a small but significant factor in structural comparison, as changes in transport distance can significantly impact results.

Fire Resistance Analysis of Two-Way Reinforced Concrete Slabs

This paper presents a fire resistance analysis of two-way reinforced concrete (RC) slabs. The study analyzes the effect of specific parameters—concrete cover thickness, span, and support conditions—on the fire resistance of the slabs. To that end, the slabs were exposed to Standard Fire ISO 834, and the 3D nonlinear numerical analyses were conducted in SAFIR2016. The results of the numerical analyses were evaluated against experimental results reported in the literature. The agreement between the two sets of results was satisfactory throughout the fire test. Nonetheless, to verify the obtained numerical results, all testing-related parameters must comply with the numerical simulation results. This comparison demonstrated the usefulness of numerical simulations in predicting the behavior of structures in fire conditions. In addition to the nonlinear numerical analysis, the fire resistance was calculated using the simplified method and tabulated data described in Eurocode 2 (Part 1.2) to assess the accuracy and reliability of fire safety regulations in the design of two-way slabs and identify significant differences between the design code and numerical analysis. The comparison showed that SAFIR2016 provides more accurate results by considering additional factors, such as tensile membrane forces, which increase the fire resistance of two-way slabs. According to the load-bearing criteria, the two-way slabs have high fire resistance, considerably higher than prescribed in the fire safety regulations, which ignore the positive effect of tensile membrane forces. According to the numerical analysis, the upper reinforcement in the compression areas of the slab's span was considered, which increased the fire resistance of the slabs. In contrast, according to the design codes, the contribution of this reinforcement is neglected. It was indicated that the increased concrete cover improves the fire resistance of the slabs. The vertical displacements increase by increasing the slab span, but according to the load-bearing criteria, all the slabs show fire resistance of over ten hours. In terms of bearing capacity, slabs with various support conditions show fire resistance of longer than ten hours. In terms of deflections, the supporting conditions of the slabs have a significant influence on their behavior. This study provides valuable insights into the fire resistance of two-way RC slabs and highlights the importance of considering specific parameters in the analysis. Doi: 10.28991/CEJ-2023-09-05-05 Full Text: PDF

TESTING OF HOLLOW-CORE END NOTCHED FLOOR SLAB

This paper examines the test results of a hollow-core reinforced concrete prestressed end-notched floor slab of formwork formation subjected to uniformly distributed load.
 The research of the end-notched slab was carrying out in the testing hall of the State Enterprise "State Research Institute of Building Structures" according to the procedure of standard DSTU B B.2.6-7.
 Vertical uniformly distributed load was applied to the end-notched slab with cross-rails and support fixtures for loading, with hydraulic jacks and pumping station equipped with force meter.
 The end-notched slab was subjected to step-by-step loading with load steps of 100 kgf/m2.
 Inspection of the surface of the end-notched slab in the test area, with recording in the register of measurement results of displacements and potential damages was carried out after every loading step.
 Vertical displacements of the end-notched slab corners were measured with four clock type indicators ICH-10. Vertical displacements of the middle slab span were measured with two deflectometers 6PAO. The middle span deflection of the end-notched slab was calculated considering corner displacements.
 Based on the results of research, it was established that before applying the load of 800 kg/m2 there were not detected cracks the opening width of which exceeded the limit values.
 The loss of loadbearing capacity of the end-notched slab was detected after the load of 1280 kgf/m2, which which exceeded the design load by 1.6 times. The end-notched slab collapsed due to loss of shear resistance.
 According to the test results, it was established that hollow-core reinforced concrete prestressed end-notched floor slab meets the requirements of strength, stiffness and crack resistance.

Influence of Skewnesson Flexural Response of RC Slab Bridges

Normally, straight slab bridges are preferred in any road network due to simplicity in design and construction. However, in some circumstances, it becomes necessary to provide the skew slab bridges owing to geometrical considerations. The structural behaviour of skew slab bridges differs significantly as compared to right slab bridges unless the skew angle is small. In this paper, attempts have been made to investigate the influence of skewness on flexural response of two-lane slab bridges of different spans ranging between 4 m to 8 m at in interval of 1 m and the skew angle has been varied from 0° to 45° in the multiple of 15°. In this study, the linear-elastic three-dimensional finite element analysis of slab bridges has been carried out using the STAAD_Pro. In order to investigate the effect of skewness on flexural response five different span slab bridges, the longitudinal moment, transverse moment, twisting moment, and the maximum deflection produced in skew slab bridges are normalized with the corresponding parameters in the right slab bridges. The study showed that the normalized longitudinal moment decreases significantly with the increase in angle of skew from 15° to 45°, in contrast, an excessive rise in the normalized transverse moments was observed.

Multi-objective green design model for prestressed concrete slabs in long-span buildings

ABSTRACT Prestressed concrete (PC) slab using tendons is one of the most frequently used slab systems in the construction of buildings with long-span slabs. To simultaneously minimize the construction cost and the environmental impact, a green design model for PC slabs in long-span structures is necessary. In this paper, a multi-objective green design model for prestressed concrete slabs (MGDPCS) was developed to minimize both CO2 emissions and the construction costs of PC slabs. MGDPCS provides the optimized PC slab thickness, diameter and yield strength of the rebar, size and yield strength of the tendon using the Non-dominated Sorting Genetic Algorithm (NSGA-II) for the input PC slab size and load. Furthermore, the effects of changes in the long- and short-side of span and tendons of PC slabs on construction costs and environmental impact are analyzed using the proposed model. Accordingly, we developed two indicators, that is, the environmental and economic scores and the eco-friendly coefficient, to evaluate the performance of the practical green designs using MGDPCS. To verify the applicability of MGDPCS, the model was applied used to analyze the designs of PC slabs in an actual six-story industrial building with a slab span of 10 m × 10 m. The results showed that the optimal designs obtained from MGDPCS outperformed existing slab designs for buildings by 8.12% and 13.62% based on the reductions in CO2 emissions and costs, respectively.

The transmission characteristics and influence prediction of impulsive vibration caused by a solid metal ball impact in buildings

The impulsive vibration induced by human running and jumping, object falling, striking during decoration, etc., significantly disturbs the learning, work, and life of people through building structure transmission. To study the influence of impulsive vibration in buildings, a vacant frame building was selected as a tested building. The vibration at each floor besides hitting spot would be measured when a solid metal ball falling freely hit the first floor of this building. The vibration response at each floor caused by the excitation above was simulated through a finite element method. The parameters of the simulation model were optimized according to measured results. Furthermore, the influence of building structure, the total amount of stories, and slab dimension on the transmission of vibration from 1 Hz to 80 Hz which can be perceived by human bodies was quantitatively studied. Results showed that the vertical weighted vibration acceleration level at each floor linearly decreased with the increase of the logarithm of the distance between each floor and the hitting spot. A prediction model of vertical weighted vibration acceleration level from 1 Hz to 80 Hz induced by the impulsive vibration in buildings was developed according to simulation results. The corrections relating to the number of story, building structure, slab span, slab length-to-width ratio, and slab thickness were respectively introduced in the model which can predict the vertical weighted vibration acceleration level at each floor above the hitting spot. The results of this study can provide a basis for the prediction and control of impulsive vibration caused by an impact source with great stiffness in buildings.

Computational design and on-site mobile robotic construction of an adaptive reinforcement beam network for cross-laminated timber slab panels

Timber slabs design is currently limited to grid layouts derived from prefabricated rectangular panels. The lack of adaptability of timber slabs to accommodate multiple span directions makes it difficult to compete with reinforced concrete slabs constructed on site. This paper describes an adaptive slab system composed of thin Cross-Laminated Timber (CLT) panels and robot-fabricated beam networks for reinforcement. The beam network was developed through intricate negotiation of structural optimization and fabrication constraints, which can adapt to changes in slab span and directions. A mobile robot platform that allows for on-site assembly of timber sticks into continuous beam networks was developed. The robot platform and slab system were tested with a case study pavilion. The co-design of the robot platform and the slab system fills the gap in on-site robotic timber construction and expands the design freedom of timber buildings.

DESIGN AND EXPERIMENTAL ANALYSIS OF BUBBLEDECK SLAB

Bubble deck, which is another name for voided slabs whose core is placed with HDPE balls that may be of different shapes and sizes is a technology that is presently procuring awareness around the world as a result of its enormous positive effects on the whole structure; this include its reduced weight, economical and mutability in terms of slab span. This research work has focused on the use of bubble deck in construction industry. Concrete grade of M35 was used. Two slabs were casted, one with HDPE Balls and the other without balls. The slab without HDPE balls (conventional slab) was casted with (78.13 kg) of concrete. On the other side the slabs with bubbles, which has spherical balls of size 60mm in which (63 kg) of concrete was used with B/H ratios of 0.48 and 49 spherical balls respectively. A total 24% of concrete was saved in the Bubble Deck slab. Considering the percentage of concrete saved, one slab was designed usually and in another a 24% reduction in dead loads was assumed and further designed was carried out. Costing of both the slab was carried out and comparison was done. In experimental analysis, destructive and non- destructive test was carried out on both the slabs and result has been compared . Key Words: RCC Slab, HDPE Balls, Reinforcement mesh.

Improvement of flexural and cyclic performance of bridge deck slabs by utilizing steel fiber reinforced concrete (SFRC)

This paper aims at investigating how the utilization of steel fiber reinforced concrete (SFRC) improves the flexural and cyclic responses of reinforced concrete bridge deck slabs. Firstly, one plain concrete slab and two SFRC slabs reinforced by mill-cut steel fibers and corrugated steel fibers, respectively, were tested under cyclic loads. The load–deflection responses, cyclic deformation behaviors, strain and crack evolutions are discussed. Subsequently, a theoretical analysis method of SFRC slab is introduced and validated. Using this method, the effects of key strength parameters of SFRC, i.e. fL, fR1, fR4, on load–deflection responses and deck slab design indices (i.e. slab height, areas of steel rebars, slab span) are clarified through parametric analysis. Results demonstrate that using SFRC in deck slabs significantly enhances the cyclic deformation performance, decreases the residual strain in the slab section, and improves the crack behavior by reducing residual crack width and increasing cracking stiffness. An increase in fL and fR1 can enhance service capacity Ps and flexural stiffness ks, as well as improve design indices under the service requirement, whilst the influences of fR4 are minor. Increasing fR1 and fR4 can enhance ultimate capacity Pu and improve design indices under the ultimate requirement, whereas the effects of fL are rather limited. Since the use of mill-cut steel fibers produces higher fL and fR1 than corrugated steel fibers, the former has better advantages to enhance Ps and ks. These results may provide references for the application of SFRC in bridge deck slabs.

Analysis of Mechanical Properties of Long-span Reinforced Concrete Composite Slabs under Different Splicing Methods

Based on the long-span slab in an assembled building project, ABAQUS is used to simulate the mechanical properties and failure modes of the slab under the condition of the whole span cast-in-place slab and the two-way rebar truss composite slab (hereinafter referred to as composite slab) with different splicing methods, in which the slabs adopt fixed support and the slab loads are uniformly distributed load. The finite element simulation results show that the integrity and mechanical properties of the whole span cast-in-place slab are not different from those of the parallel splicing two-way composite slab, but they are obviously better than the parallel cross splicing two-way composite slab; In the same slab span, the cast-in-place seam of the composite slab in the middle cracks first due to stress concentration, and with the increase of the uniformly distributed load of the slab, the crack will pass through the cast-in-place seam and develop to the composite slab on both sides, and finally all the concrete at the bottom of the slab will crack and fail. According to the simulation results, the following suggestions are given: if the truss rebar composite slab is adopted for the long-span slab, the two-way composite slab should be adopted, and the cast-in-place seam should be arranged in the direction of less stress, and the seam should not be arranged in both directions.

Prediction of bending performance for a separable CLT-concrete composite slab connected by notch connectors

In this study, the bending performance of a separable cross-laminated timber (CLT)–concrete composite slab for reducing environmental impact was investigated. The slab has consisted of CLT and eco–concrete, and round-notch shape shear connectors resist the shear force between the CLT and eco-concrete. The eco–concrete was composed of a high-sulfated calcium silicate (HSCS) cement, which ensures low energy consumption in the production process. The bending stiffness and load-carrying capacities of the slab were theoretically predicted based on the shear properties of the notch connectors and validated with an experimental test. The shear properties of two types of notch shear connectors (Ø100 mm and Ø200 mm) were measured by planar shear tests. As a result, the stochastically predicted bending stiffness of the slab (with Ø100 mm shear connector) was 0.364 × 1012 N mm2, which was almost similar to test data. The load-carrying capacities of the slab were governed by the shear failure of the notch connectors, and the lower fifth percentile point estimate (5% PE) was 21.9 kN, which was 7.9% higher than the prediction (20.2 kN). In a parameter study, the effect of notch diameter for the CLT-concrete slab span was analyzed depending on the applied loads, and the maximum spans of the slab with Ø100 mm notch or Ø200 mm notch were not significantly different.

Finite element analysis of bubble deck slab with various thickness of HDPE bubble

Deflection of the slab is the most important parameter by which we can calculate the depth of the slab which depends on the total loads applied on the slab the and span of the slab between two columns. The concept of a bubble slab in which middle layer concrete is replaced by HDPE bubble will help to reduce its self-weight, deflection, moments & force reactions. The criteria of choosing a suitable thickness of HDPE bubble are well mentioned in this paper with suitable examples so we can easily use that thickness value in practical on-site. Static analysis of several models is done by finite element analysis method with tetra meshing by using Ansys ver. 15.0 as an analyzing tool. In this paper, results clearly specify the structural behavior change of bubble slab by changing its HDPE bubble thickness as well as it also specifies the best thickness value of HDPE bubble. A bubble slab will be more useful on those structures in which intermediates columns is not required when the span of a conventional slab is large, then its deflection, moments & force reaction values is greater, by which its depth is increased which makes the conventional slab heavy so its total self-weight loads are transferred to column to footing which makes both increases in size & uneconomical. It is evident from the analysis that a typical 150 mm thick slab consumes more than 149.8 kg of concrete than a bubble slab and produces a large deflection, on the other side a bubble slab with a 2 mm HDPE bubble can save 63.04% more deflection. As per analysis, it can be concluded that 2 mm thickness of HDPE bubble is the optimum thickness of HDPE bubble used for bubble slab. If we used the concept of bubble slab our nearly 35% self-weight of the slab is reduced which positively affects on load transfer to other structural members and by this procedure whole structure will be more stable, durable & economical.